Crystal Structure of CsLnFe(CN) sub 6 5H sub 2 O (Ln=Ce, Pr Nd), CsCeFe(CN) sub 6 4H sub 2 O, and TlT mRu(CN) sub 6 3H sub 2 O

We have investigated the crystal structures of CsLnFe(CN) sub 6 nH sub 2 O (Ln=lanthanide, n=4m5), as well as TlTmRu(CN) sub 6 3H sub 2 O. These phases can be thought of as derivatives of LnFe(CN) sub 6 4H sub 2 O, where, simultaneously, an alkali ion (or Tl sup +) is introduced while the valence of Fe is reduced from Fe sup (3+) to Fe sup (2+). A new arrangement of hte structural units is observed in the CsLnFe(CN) sub 6 5H sub 2 O, where the corrdination of the Ln-ion is changed to a bisdisphenoid. The resulting LnN sub 5 O sub 3 units alternate with Fe(CN) sub 6 units to form an overall rocksalt-type ralted lattice that accommodates the alkali ions in interstitial sites. Due to the arrangement of the water molecules, a layer structure results.